prevent 2 end points of rhumb line from overlapping
prevent 2 end points of rhumb line from overlapping

likangning93/cesium,AnalyticalGraphicsInc/cesium,likangning93/cesium,CesiumGS/cesium,CesiumGS/cesium,AnalyticalGraphicsInc/cesium,CesiumGS/cesium,likangning93/cesium,likangning93/cesium,likangning93/cesium,progsung/cesium,CesiumGS/cesium,progsung/cesium,CesiumGS/cesium